Locate the starter. Have someone hold your key to the ON position. As
they hold the key, rap on the starter with a hammer. If the truck suddenly
turns over, your starter is bad. If that doesn't work, try starting the truck
in neutral. You may have a bad neutral safety switch. Post back with
results......

That's good advice. But if battery cables are good, does the red led anti-theft stop flashing when you insert key? If not, the immobilizer might have lost it's programming and key is not communicating with ECU

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